Ai conversion of a Nikkor-P 105mm f/2.5

[chris dees]

Not quite Chris, you have an original Ai ring on

Her is how it looks, cleaned and lubed as well

Nah... with the AI-ring it looks even better/sexier.

[Erik Lund]

Thanks, a very nice sample of the first 105mm 2.5 Nikkor F lenses.

First I mark how much to remove to clear the tap on the camera mount. For this aperture ring a tiny bit more than 1.6mm needed to be cut off, so ample room for the screws for the ears,  then I tighten the screws on the ears so I'm confident they are absolutely tight.

Then I 'saw' off the two rear pieces that needs to come off with a Diamond disc on the Proxxon milling machine, this disc leaves a very fine surface, I finish off all edges with a needle file.

[Akira]

Thanks, Erik, for the details of the procedure.  It is still awesome after knowing how you did it.

[MFloyd]

Thanks again to Erik & Bjørn. I'm eagerly waiting to mount the lens and take some pictures.

[Bjørn Rørslett]

Just remember this is *not* an AIS lens and thus you have to use the aperture ring on the lens. As the Nikons use aperture setting by camera dial as their default, you do need to change that behaviour in the Custom Settings menu.

Be aware that if you keep the default setting you'll get an error message 'FEE' on the camera that can be eliminated by putting the lens to its minimum aperture setting, f/32 in this case. However, although the meter reading will be correct, the resulting exposure will be off because the camera is tricked by the non-linear aperture of the lens. Thus, operate the system in the old manner by rotating the aperture ring and all will work just fine. Metering is still correct as before, but now the exposure will be likewise as well.

[MFloyd]

With regard to Björn's recommendation and for the D5, go to f4 "Controls"; "Customize command dials"; "Aperture settings"; select "Aperture ring"

For the D610 same procedure but by selecting f5; for other body's, you should look into it.

With regard to the non-linear aperture of the Nikkor-P 105mm f/2.5, I made a quick test run through all the apertures by dialing with the two methods (aperture ring & body-dial): if there is any difference, it should be minimal; I will have to measure it further.

Anyway, the double transformation (chip and Ai) is a real success.  Thank you again, Erik & Bjørn. 

[Erik Lund]

Thank you! Nice to hear your satisfied;)

[MFloyd]

Herewith, the first (non technical) picture of the 105mm f/2.5's second life:

[Hugh_3170]

Well the 105mm f/2.5 is well known for its qualities as a portrait lens - just that this time the subject is your dog!   

Certainly sharp enough eyes.

A solid citizen indeed.  Does he specialise in death by licking?   

[MFloyd]

....  Does he specialise in death by licking?   

and at ISO 11'400 (D5)...

[the solitaire]

Awesome!  How could you keep the rabbit ears attached to the trimmed aperture ring with the screw holes and the screws altogether?!

You need to trim the rabbit ears as well as the screws because both will interfere with the Ai indexing tab on th ecamera mount.

I also just leave them on when converting lenses rather then shave the aperture ring and rabbit ears seperately, then attach the screws and trim shave a little off as well.

Personally i just remove a fraction less material so the thread of the screws holding the rabbit ears does not show. I am certain Erik did not cut the aperture ring open up to the thread. This profile shows when leaving a paper thin layer of material there and then screw in the rabbit ears.

[Hugh_3170]

Lenses that are going to be used on modern cameras don't need the rabbit's ears and they look just fine without them.  Actually the rabbits ears are like rabbits themselves - a dammed nuisance, especially if they accidentally come up against anything delicate they can cause damage.  I certainly don't quite cut into the holes.  Normally I paint the cuts with etch primer and matt black enamel paint to finish.

[Bjørn Rørslett]

If they are used with post-1977 cameras, agree that these old lenses do well enough without their rabbit ears. For the widest range of compatibility, however, I let the rabbits stay put myself.

[the solitaire]

I agree that the rabbit ears are not needed for metering. I do still find them very convenient because I can use them for orientation when chosing the aperture. I also use them for orientation when mounting lenses. At f5,6 the rabbit ears are at the same location as the black dot which tells you in which position to mount the lens.

So all in all, even though they do not interact with thecamera, they interact with me and allow me to perform a lens change and/or aperture change blind. Reason enough for me to keep them on there

[Erik Lund]

I cut into the threads of the rabbit ear screws,,,